1. Field of the Invention
The present invention relates generally to printing presses and more particularly to a device and method for setting a lap on the folded signature.
2. Background Information
Web printing presses print a continuous web of material, such as paper. In a folder of the printing press, the continuous web then is cut into signatures in a cutting unit and folded.
One way to fold the resulting signatures is using a rotary blade folder, which includes a cylinder with rotary blades which selectively extend beyond the circumference of the cylinder to provide a fold to the signature. The signature is held at a lead edge by pins, and folded, usually near the middle of the signature by a fold blade. The fold is forced by the blade toward two rotating folding rollers located beside the cylinder, which grip the signature along the fold at a nip, set the fold and deliver the folded product, for example, to a fan unit. Chapter 6 (pages 136 to 154) of the book xe2x80x9cNewspaper Pressesxe2x80x9d by William Braasch, for example, describes rotary blade folders.
If the signature is folded perfectly in half, no lap, which is the distance between the front and lead edges of the signature, results. However, if the signature is folded off-center a lap results, since the front and lead edges are spaced apart.
With rotary blade folders, the lap changes when the speed of the machine changes. Thus during slower a pre-production test run, the lap will be different than during a full speed production run. Proper measurement adjustment of the lap in the rotary blade folder while the folder is running thus is important.
The lap of the signature may be adjusted by moving the blades circumferentially with respect to the pins. The distance between the pin and lead edge of the signature and the location where the rotary blade forces the signature into the folding unit determines the lap.
The abstract of Japanese Patent Application No. 62-70174 purports to disclose a helical gear mechanism to adjust the lap quantity of folded sheets without stopping the machine. Separately formed needle segments and folding edge segments are provided in turn on a folding barrel. The needle side helical gears are shifted in an axial by a rotating drive mechanism.
The device of the abstract of Japanese Patent Application No. 62-70174 appears not have a controller unit for directing the lap adjustment mechanism and the device seems incapable of self-correcting the lap. Moreover, no optical sensor and no feedback mechanism to sense a lap appear to be present.
The abstract of Japanese Patent Application No. 6-255881 purports to disclose a lap adjusting data corresponding to each rotary press speed of each longitudinal page that is fed as a command signal to an operating motor of a control unit. A deviation of a motor rotational speed detection signal from the above command signal is fed as a command signal to the operating motor and the rotational speed is controlled until a lap is obtained within a permissible range.
The device of Japanese Patent Application No. 6-255881 has the disadvantage that no sensors appear to be present to automatically detect the lap on a folded signature. Thus, although the device appears capable of adjusting the lap on a folded signature pursuant to command signals, the device appears not to have a feedback mechanism capable of checking the actual lap on a folded signature.
An object of the present invention is to provide for a device and method for measuring and controlling a lap on folded signatures. An additional or alternative object of the present invention is to provide an optical sensor and a controller for measuring and setting a lap on the folded signatures. Yet another additional or alternative object of the present invention is to provide an automatic feedback mechanism to automatically adjust the lap on the folded signatures.
The present invention provides a folder system comprising an adjustable-lap folder for folding signatures so as to form folded signatures, an optical sensor for measuring a lap on the folded signatures, and a controller connected to the folder and the optical sensor for adjusting the lap.
Preferably, the adjustable-lap folder is a rotary blade folder having folding rolls for accepting the signatures so as to form folded signatures.
The rotary blade folder may further include an outer pin shell circumferentially movable with respect to blades of the rotary blade folder. The outer pin shell provides the advantage of automated adjustment of the location of the signature with respect to the folding blades so that the location of the fold may be changed.
The optical sensor may sense the first edge (the folded edge) of the folded signature to send a signal to the controller when the folded edge passes the optical sensor. When the folded edge of the folded signature passes the sensor, the optical sensor is triggered. The sensor may be triggered by a break in an electromagnetic beam that emanates from the optical sensor. When the beam connects again, the last edge (either the trail or lead edge of the signature) is detected. Hence, the amount of time, t, that it takes for the entire signature to pass the optical sensor is known. The triggering of the optical sensor provides the advantage of automatic and efficient data accumulation, which may be used in calculating the lap of the folded signature.
Preferably, the controller has a processor to receive the velocity of the folded signature and to receive the signals sent by the optical sensor to determine a length of the folded signature, s. When the optical sensor is triggered, the optical sensor sends a signal to the controller. Hence, an amount of time, t, necessary for the folded signature to pass may be calculated. For example, the controller could start an internal timer after receiving the first signal and stop the timer after receiving a second signal. The amount of time, t, is multiplied by the velocity, v, of the signature, which is a pre-determined constant, to give the length, s, of the signature, s=t*v. The velocity may be determined by the rate of rotation of the folding rolls.
Preferably, the processor uses the length, s, of the folded signature and a cutoff size of the signature, c, to calculate the lap of the folded signature, D. To calculate the lap of the folded signature, D, the length of the signature, s, is multiplied by two, from this quantity the length of the cutoff, c, is subtracted, D=(s*2)xe2x88x92c. The cutoff, c, is the length of the entire paper and is determined from the size of the signatures cut by a cutting cylinder from a web. The calculation provides the advantage of automatically determining the correct lap on the folded signature without the need for an operator to measure the lap.
Preferably, the processor may compute whether the lap is positive or negative, i.e., the lap sign, based on a lap of a subsequent folded signature and the previously computed lap. The computation provides the advantage of determining the lap sign without the need for the machine to be stopped or an operator to be present. Moreover, the data obtained may be used to automatically adjust the device to accord with an operator specified lap distance.
The lap sign determination may be performed by comparing the lap on a primary folded signature to the lap on the subsequent folded signature. The absolute value of the primary lap is first determined and the controller then sends a control signal to circumferentially move the outer pin shell a small distance with respect to the folding blade shell, e.g., by increasing the distance between the pin and the folding blade for one signature. The outer pin shell thus rotates circumferentially with respect to the pin shell a small distance, preferably so that the difference between the primary lap and a subsequent lap is equal to the minimum distance that the optical sensor is able to record, but in any event less than the primary lap. If the lap of the primary signature is positive, the increase in distance between the pin and the folding blade will decrease the lap of the subsequent signature. If the lap of the primary signature is negative, the increase in distance will increase the absolute value of the lap of the signature. The sign of the lap of the primary signature thus can be determined. It should be noted that the lap on the primary signature could also be zero, in which case a sign determination is not necessary.
As an example, if the outer pin shell circumferentially rotates with respect to the blade shell, e.g., clock-wise, to increase the distance between a pin and the folding blade, the controller may then compare the subsequent lap D2 with the primary lap D1 to determine the sign of the primary signature. If the difference between the primary lap D1 and the subsequent lap D2 is a positive number, i.e., D1xe2x88x92D2 greater than 0, the primary signature has a positive lap sign. Conversely, if the difference between the primary lap D1 and the subsequent lap D2 is a negative number, i.e., D1xe2x88x92D2 less than 0, the primary signature has a negative lap sign.
The outer pin shell could just as easily be rotated circumferentially with respect to the folding blade shell so as to decrease the distance between the pin and the blade, e.g., counter-clock-wise. The controller may then compare the subsequent lap D2 with the primary lap D1 to determine the inclination of the primary signature. If the difference between the primary lap D1, and the subsequent lap D2, is a negative number, i.e., D1xe2x88x92D2 less than 0, the primary signature has a positive lap sign. Conversely, if the difference between the primary lap D1 and the subsequent lap D2 is a positive number, i.e., D1xe2x88x92D2 greater than 0, the primary signature has a negative lap sign.
Preferably, the controller has an automatic feedback capability to use the lap data and positive or negative signature inclination data to automatically configure the lap on the folded signature pursuant to an user specified lap. Setting of the lap is accomplished by moving the outer pin shell in relation to the folding blades depending on a control signal sent by the controller. In order to determine the correct control signal, the controller determines the sign (if not already known) of the folded signature and then compares the lap on the folded signature to a desired lap entered prior by an operator. The comparison provides the advantage of automatic adjustment of the lap on the folded signatures to accord with an user specified lap without stopping of the folder.
The feedback control can be performed by comparing the primary lap D1 with a desired lap x1 input by the operator. The desired lap x1 may be a positive, negative, or zero value.
The controller then makes a determination of whether the primary signature has a positive or negative sign, or zero, and moves the outer pin shell the desired amount by circumferentially rotating the pin shell with respect to the blade shell.
When the primary signature has a positive lap sign, if the primary lap D1 is greater than the desired lap x1, the control unit sends a control signal that causes the outer pin shell to circumferentially move so that the distance between the pin and the folding blade increases. However, if the primary lap D1 is less than the desired lap x1, the control unit sends a control signal that causes the outer pin shell to circumferentially move so that the distance between the pin and the folding blade decreases.
Preferably, the folding cylinder includes at least one pin attached to an outer pin shell to hold the lead edge of the signature.
Preferably, the rotary blade folder may further comprise a cutting cylinder and an anvil attached to the outer pin shell to aid in cutting the web.
The present invention provides a method for folding signatures comprising cutting a web with an adjustable-lap folder so as to form signatures; folding the signatures using the folder so as to form folded signatures; measuring optically a lap in the folded signatures; and adjusting the lap as a function of the measuring step.
The folding step may further include pinning a lead edge of a signature and contacting the signature at a set distance from the lead edge with a folding blade. By pinning the lead edge and contacting the signature a set distance from the lead edge, the signature is stabilized and the lap distance may be determined.
Preferably, the method for folding signatures may include measuring a velocity of the folded signatures. The velocity measurement allows the lap distance to be determined if the speed of the rotary blade folder is changed.
Preferably, the method for folding signatures may further include altering the set distance so as to change the lap. The advantage provided by changing the set distance is that the lap distance of a signature may be changed.
The step of altering the distance may preferably include altering the set distance by using a feedback from a controller. By using the feedback from the controller, the advantage of automatic calibration of the lap distance is provided.